Re: [PATCH 1/5] mm/vmalloc.c: correct a few logic error for __insert_vmap_area()

From: zijun_hu
Date: Wed Sep 21 2016 - 18:35:52 EST

On 2016/9/22 5:10, David Rientjes wrote:
> On Wed, 21 Sep 2016, zijun_hu wrote:
>> From: zijun_hu <zijun_hu@xxxxxxx>
>> correct a few logic error for __insert_vmap_area() since the else
>> if condition is always true and meaningless
>> in order to fix this issue, if vmap_area inserted is lower than one
>> on rbtree then walk around left branch; if higher then right branch
>> otherwise intersects with the other then BUG_ON() is triggered
> Under normal operation, you're right that the "else if" conditional should
> always succeed: we don't want to BUG() unless there's a bug. The original
> code can catch instances when va->va_start == tmp_va->va_end where we
> should BUG(). Your code silently ignores it.
Hmm, the BUG_ON() appears in the original code, i don't introduce it.
it maybe be better to consider va->va_start == tmp_va->va_end as normal case
and should not BUG_ON() it since the available range of vmap_erea include
the start boundary but the end, BTW, represented as [start, end)

this patch correct the logic to that mentioned in the comments, it maybe be
more logical and more understandable